It is the major aim to relate the Epstein-Barr virus to the etiology of Burkitt's lymphoma, nasopharyngeal carcinoma, and pottibly other human malignancies, mainly by serologic approaches. It is proposed to continue ongoing long-term studies of patients to correlate changes in the spectra and titers of antibodies to EBV-determined antigens with clinical events, prognosis, and effectiveness of therapy. New test procedures will be developed, especially for measuring immune responses to EBV-transformed cells, which might contribute to understanding of the pathogenesis of EBV-associated malignant and non-malignant diseases and of the biology of the virus.